Binary evolution in Stellar systems

Three new star cluster models containing 250 members and one case with 500 particles have been studied by numerical methods of direct integration. The evolution is dominated by one central binary in all systems with a realistic mass spectrum and more than 50% of the total energy is absorbed by one heavy pair after only 6–18 mean crossing times. General conditions for binary formation and disruption are discussed and a qualitative explanation is given for the energy sink behaviour. Strong interactions with close binaries lead to increased relaxation and the ejection of energetic escapers. At the same time the corresponding recoil kinetic energy is transferred to the other central members by two-body encounters which prevent a secondary phase of central contraction.